1. Field of the Invention
The present invention relates to a positive photosensitive resin composition for spray coating for forming a coating film by spray coating on the inner surface of a hole provided in the thickness direction of a semiconductor wafer. Further, the present invention relates to a method for producing a through electrode for electrically connecting an integrated circuit provided on the surface of a semiconductor wafer and a connecting terminal provided on the back surface of the semiconductor wafer, comprising the step of forming a coating film pattern on the inner surface of a hole using the composition.
2. Discussion of the Background
Recently, as the need for high-functional performance and miniaturization of electronic devices has been increased, the technique for high-density package of semiconductor integrated circuits has been developed. As one of such packaging techniques, attention is focused on the three-dimensional packaging technique in which a semiconductor integrated circuit is laminated using a through electrode formed in the thickness direction of a semiconductor wafer.
As a method for forming a through electrode, for example, a method in which: an insulating film is formed on the inner surface of a non-through hole provided on the surface of a semiconductor wafer; the interior of the hole is filled with an conductive material; after that, the semiconductor wafer is shaved from the back surface side (back grind); and thereby the conductive material embedded in the hole is exposed, is known (for example, see Japanese Laid-Open Patent Publication No. 2006-147873; and Japanese Laid-Open Patent Publication No. 2008-91857). However, this method requires a high cost since it is necessary to make a deep hole in a thick wafer in order to carry out back grind later. In addition, there is a limitation on the ratio of depth/diameter of a hole (aspect ratio) that can be formed in a semiconductor wafer. In order to make a deep hole, a large diameter is required. It is impossible to make many holes at narrow intervals, and there are wasteful areas.
Meanwhile, a method in which: an integrated circuit is formed on the surface of a semiconductor wafer; after that, a hole, which passes through from the back surface of the semiconductor wafer to reach the integrated circuit on the surface of the semiconductor wafer, is made; an insulating film is formed to cover the inner surface of the hole; an electrode portion of the integrated circuit is exposed; and after that, an conductive material is embedded, thereby forming a through electrode, is known (for example, see Japanese Laid-Open Patent Publication No. 2007-305955).
Conventionally, in the case where an integrated circuit is formed on the surface of a semiconductor wafer and thereafter a hole which reaches the back surface of an electrode portion of the integrated circuit is provided to form a through electrode, a method in which a SiO2 film is formed on the inner surface of the hole using the vapor deposition method and thereafter the SiO2 film on the back surface of the electrode portion is subjected to etch back, thereby exposing the back surface of the electrode portion, is used. However, it is difficult to form a vapor-deposited film having a uniform thickness on the inner surface of a very small-sized hole having a high aspect ratio, and the thickness of the vapor-deposited film at the deep portion of the hole becomes thinner. Therefore, at the time of etch back, a part of the film is etched to expose a metal wiring, a conductive portion of semiconductor wafer or the like, and leakage current is generated to cause decrease of a yield rate.
Meanwhile, methods for forming an insulating film by spray coating have been suggested. For example, in Japanese Laid-Open Patent Publication No. 2006-147873, a method for forming an insulating film on the inner wall of a hole formed in the thickness direction of a semiconductor wafer by spraying a mist comprising an insulating material from a spray nozzle with the average diameter of the mist being changed is suggested. However, the type of an insulating material must be selected in consideration of adhesion to wall surfaces, heat resistance, electrical insulation property, etc. A selected material may not be solved in a diluting solvent appropriate for spray coating or may be degenerated. It is difficult to form a coating film having a uniform thickness on the inner surface of a hole of a semiconductor wafer only by employing an original idea for a coating method.